U.S. patent application number 12/011769 was filed with the patent office on 2008-09-25 for electric fault current limiter having superconducting elements inside a cryogenic vessel and bushings for connecting an external circuit.
Invention is credited to Joachim Bock, Frank Breuer, Werner Kohler.
Application Number | 20080232014 12/011769 |
Document ID | / |
Family ID | 38093031 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080232014 |
Kind Code |
A1 |
Bock; Joachim ; et
al. |
September 25, 2008 |
Electric fault current limiter having superconducting elements
inside a cryogenic vessel and bushings for connecting an external
circuit
Abstract
Electric fault current limiter has superconducting elements
inside a cryogenic vessel and bushings for connecting an external
circuit. The electric fault current limiter (1) includes a
cryogenic vessel (2) and superconducting assemblies (5) including
high temperature type superconducting elements (HTSC) immersed in a
liquid coolant (6) such as liquefied nitrogen. Bushings (25, 28)
with conductors (17, 18) are associated with a main body (3) of the
vessel (2) such that the conductors (17, 18) extend horizontally
from a surrounding space into an ullage space (8) situated between
a level (7) of the liquid coolant (6) inside the vessel (2) and a
cover (4). The arrangement of the bushings (25, 28) according to
the invention allows for removing the cover (4) without dismantling
electrical connections between the current limiter (1) and a
circuit to be protected as is necessary with prior art
limiters.
Inventors: |
Bock; Joachim; (Erftstadt,
DE) ; Breuer; Frank; (Bonn, DE) ; Kohler;
Werner; (Berlin, DE) |
Correspondence
Address: |
SOFER & HAROUN LLP.
317 MADISON AVENUE, SUITE 910
NEW YORK
NY
10017
US
|
Family ID: |
38093031 |
Appl. No.: |
12/011769 |
Filed: |
January 29, 2008 |
Current U.S.
Class: |
361/58 |
Current CPC
Class: |
H01F 6/04 20130101; H01F
6/065 20130101; Y10S 505/885 20130101 |
Class at
Publication: |
361/58 |
International
Class: |
H02H 9/00 20060101
H02H009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2007 |
EP |
07300797.3 |
Claims
1. An electric current limiter comprising: a cryogenic vessel
having a main body and a cover, both defining an inner space
separated from a surrounding space; superconducting elements of the
HTSC type immersed in a cryogenic liquid contained in the inner
space of the vessel; an ullage space between the cryogenic liquid
and the cover; and bushings with conductors extending from the
inner space of the vessel to the surrounding space, the conductors
connecting the superconducting assemblies with a current path to be
protected against a fault current, wherein the bushings are
positioned in an area of the main body of the vessel surrounding
the ullage space underneath the cover.
2. The electric current limiter according to claim 1, wherein
bushings are positioned in opposed wall parts of the main body of
the cryogenic vessel and that the conductors of the bushings extend
horizontally into the ullage space.
3. The electric current limiter according to claim 2, wherein the
wall parts of the main body are designed as cylindrical extensions
housing the bushings and that a flange is provided at the end of
each extension for coupling ongoing electrical equipment.
4. The electric current limiter according to claim 3, wherein the
flange of one of the extensions is adapted to a component for
outdoor use and the flange of the other extension is adapted to
indoor equipment.
5. The electric fault current limiter according to claim 1, wherein
the bushings are disk-type elements with concentrically arranged
inner conductors.
Description
RELATED APPLICATION
[0001] This application claims the benefit of priority from
European Patent Application EP 07 300 797.3, filed on Feb. 16,
2007, the entirety of which is incorporated herein by
reference.
DESCRIPTION
Field of the Invention
[0002] The invention relates to an electric current limiter
comprising a cryogenic vessel enclosing an inner space with the
superconducting elements and the cryogenic liquid for cooling the
superconducting elements.
BACKGROUND
[0003] In general, a cryogenic assembly is described in WO
03/044424 A2 for cooling superconducting elements, said cryogenic
assembly being suitable for a plurality of low temperature
applications such as magnetic resonance imaging, superconducting
transformers, fault current limiters etc.
[0004] The superconducting elements are housed in an interior
vessel filled with the cryogenic medium, i.g. liquid helium. The
interior vessel is enclosed in a cryostat with an insulating
evacuated intermediate space defined by the outer wall of the
cryostat housing and the outer wall of said interior vessel.
[0005] For electrical connection of the superconducting elements
with the warm surrounding of the cryostat a neck tube is provided
extending from the interior vessel into the evacuated intermediate
space of the cryostat. Further, insulated external terminals are
provided in the outer wall of the cryostat for allowing passage of
an electric cable for electric connection of the neck tube with the
warm surrounding of the cryostat. By this assembly electrical
connection of the superconducting elements within the interior
vessel with the warm surrounding of the cryostat is possible via
the neck tube without the need of opening of the neck tube which is
to be avoided in order not to admit air to the interior vessel.
[0006] In particular, the present invention relates to an electric
current limiter comprising [0007] a cryogenic vessel having a main
body and a cover, both defining an inner space separated from a
surrounding space, [0008] superconducting elements of the HTSC type
immersed in a cryogenic liquid contained in the inner space of the
vessel, [0009] an ullage space between the cryogenic liquid an the
cover, [0010] and bushings with conductors extending from the inner
space of the vessel to the surrounding space, the conductors
connecting the superconducting elements with a current path to be
protected against a fault current.
[0011] A current limiter of the HTSC-type mentioned before, where
HTSC stands for High Temperature Superconductor, is described in a
publication entitled "Fault current limiter in medium and high
voltage grids" by Dr.-Ing. Martin Kleimaier and Prof. Dr.-Ing.
Claus Neumann that was presented at "IEA Workshop on Electricity
Transmission and Distribution Technology and R&D" in Paris,
France, on 4-5 Nov. 2004. Also in this publication there is
described the technical background for understanding the general
purpose and the considerable value of current limiters in
transmission and distribution networks.
[0012] The cryogenic vessel of the superconducting current limiter
according to the publication mentioned above is closed to the
surrounding atmosphere by a cover that carries all the elements
necessary for the operation of the device such as pipes for
transferring a cooling liquid into the vessel for maintaining the
superconducting state and bushings having conductors for the
connection of the superconducting elements inside the vessel to an
external circuit which is to be protected against a fault current.
In case the current limiter has to undergo inspection or service
work at least all electrical connections between the conductors of
the bushings and the external circuit have to be dismantled prior
to removing the cover of the cryogenic vessel. This is necessary in
contrast to pipes or hoses used for carrying the cooling liquid
which can be made from flexible material because conductors adapted
to a high fault current are exposed to considerable mechanical
forces and thus can only be designed as solid parts.
OBJECT AND SUMMARY
[0013] Considering the situation described before it is the aim of
the invention to make integration of a superconducting current
limiter into existing or new substations or switchgear and related
service work much simpler.
[0014] According to the invention the bushings are positioned in an
area of the main body of the vessel surrounding the ullage space
underneath the cover. This means that removing the cover of the
cryogenic vessel does not necessitate dismantling of electrical
connections and is not complicated by the weight of the bushings
and their associated conductors.
[0015] The invention can be put into practice in a number or
favourable ways both for indoor and outdoor substations or
switchgear.
[0016] In a first embodiment of the invention the bushings are
positioned in opposed wall parts of the main body of the cryogenic
vessel and that the conductors of the bushings extend horizontally
into the ullage space. This design provides aligned electrical
connecting facilities favourable for all conceivable applications
of the current limiter.
[0017] On the other hand it may be desirable to maintain the
position or orientation of electrical connecting facilities of
prior art devices. This can be achieved according to a further
embodiment of the invention which is characterized by the feature
that the wall parts of the main body are designed as cylindrical
extensions housing the bushings and that a flange is provided at
the end of each extension for coupling ongoing electrical
equipment. The cross section of the extensions may preferably be
cylindrical, but other forms may be chosen if appropriate.
[0018] In high voltage systems it is known to use transmission
lines having towers and conductors positioned in normal atmospheric
air and to use gas-insulated equipment with small dimensions for
switching and distribution purposes. According to a further
embodiment of the invention the current limiter can be used as a
coupling and protecting element in systems employing different
types of insulation. This can be achieved by the fact that the
flange of one of the extensions is adapted to a component for
outdoor use and the flange of the other extension is adapted to
indoor equipment. In all of the mentioned embodiments bushings of a
disk-type design having a concentrically arranged inner conductor
may be used. Examples of bushings suitable for the purposes of the
invention are described in DE 23 60 071 C2 and DE 28 48 560 C2.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The invention will now be explained in more detail with
reference to the drawings, in which:
[0020] FIG. 1 is a side elevation of a first embodiment of a
current limiter according to the invention particularly adapted for
the use with cables.
[0021] FIG. 2 is a top view of the current limiter shown in FIG. 1,
with cryogenic components external of the limiter cut off.
[0022] FIG. 3 shows a second embodiment of a current limiter useful
for connection to overhead lines, also in a side elevation,
[0023] FIG. 4 is top view of the current limiter shown in FIG. 3
without cryogenic components external of the limiter,
[0024] FIG. 5 is a side elevation of a third embodiment of a
current limiter which is a coupling link between an overhead line
and a gas-insulated substation, and
[0025] FIG. 6 is to view of the limiter shown in FIG. 5, external
cryogenic components being omitted.
DETAILED DESCRIPTION
[0026] Referring to FIG. 1 of the drawings, a current limiter 1
comprises a cryogenic vessel 2 having a main body 3 and a cover 4.
In the manner known with prior art current limiters superconducting
elements 5 are immersed in a volume 6 of a coolant such as
liquefied nitrogen the level of which is designated by numeral 7.
Above the level 7 and beneath the cover 4 there is an ullage space
8. The cover 4 is fitted with pipes 9 and 10 for filling coolant
into the vessel 2 and for controlling pressure. There may be
provided further pipes or ducts in the cover 4 if necessary or
appropriate depending on a suitable type of a coolant supply system
provided for the operation of the current limiter. For the purpose
of illustration a coolant supply system 34 is shown as a unit in
FIG. 1. The mentioned cryogenic components external of vessel 2 are
not shown in FIG. 2 so as to simplify the drawing.
[0027] In the current limiter according to FIG. 1 connections to a
current path to be protected against a fault current are made by
cables 11 and 12 the terminations 13 and 14 of which respectively
are placed in housings 15 and 16. Whereas the orientation of the
terminations 13 and 14 is vertical conductors 17 and 18 associated
to the terminations 13 and 14 are orientated horizontally and
extend into the ullage space 8 of the vessel 2. Connectors 19 and
20 are provided for connecting terminations 13 and 14 to conductors
17 and 18. There are also provided inner connectors 21 and 22 for
completing the current path through the cables 11 and 12 and the
superconducting assemblies 5.
[0028] In the embodiment of FIG. 1 conductor 17 passes through
disk-type bushings 23 and 24 the first of which is fitted to
housing 15 and the latter of which is seated in a horizontal
extension 25 of main body 3 of the vessel 2. Disk-type bushings 23
and 24 may be of a design applicable in high-voltage equipment and
may be adapted to the use with temperatures existing in
superconducting systems by proper choosing of materials. Housing 15
is joined to extension 25 by means of flanges 26 and 27. On the
side of the vessel 2 opposite to conductor 17 there are provided
two more disk-type bushings 28 and 29 the distance of which is
chosen to accommodate in between a disconnecting switch 30 shown in
the disconnected state. Also, the length of a further extension 31
of main body 3 is designed correspondingly. Housing 16 and
extension 31 are joined in the same manner as already explained for
extension 25 and housing 15 by means of a flange 32 fitted to
extension 31 and flange 33 fitted to housing 16. Conveniently, in
disconnecting switch 30 there is provided an axially moving contact
for interrupting or closing conductor 18.
[0029] As will be noted by comparing FIGS. 1 and 2 the vessel 2 is
mainly cylindrical with a circular cross section and the bushings
23 and 24 are positioned on opposed wall parts so that the
associated conductors 17 and 18 enter into the ullage space 8
underneath the cover 4. Thus, cover 4 may easily be removed as is
shown in phantom in FIG. 1 without the need to dismantle the
electrical connections between cables 11 and 12 and superconducting
elements 5. In case flexible pipes or hoses are used for connecting
a coolant supply system 34 with pipes 9 and 10 seated in cover 4 it
may even be sufficient to remove voltage from the current limiter
by actuating disconnecting switch 30 and to cut off coolant supply
system 34 prior to removing cover 4. This will at least allow for
an inspection of the interior of vessel 2.
[0030] The current limiter shown in FIGS. 1 and 2 is a one-pole
unit so that in a conventional three-phase system three identical
units are used. This configuration is particularly applicable to
systems having a rated voltage of 110 kV or above. In the lower
range of rated voltages between 6 kV and 60 kV a three-pole design
already known for superconducting current limiters could be taken
into consideration within the scope of the invention.
[0031] A second embodiment of a current limiter 35 shown in FIGS. 3
and 4 is particularly adapted for the use with overhead lines
indicated at 36 and 37. Vessel 2 with main body 3 and cover 4 of
current limiter 35 correspond to FIGS. 1 and 2, so only features
specific to the line-type application will now be described. As is
the case with the embodiment shown in FIGS. 1 and 2 disk-type
bushings 38 and 39 with associated conductors 40 and 41 are
provided in opposite wall parts of main body 3 designed as
extensions 42 and 43. Both extensions are fitted with a flange 44
and 45 respectively which correspond to flanges 46 and 47 of
outdoor bushings 48 and 49 suitable for high-voltage applications.
Bushings 48 and 49 are shown positioned with a certain inclination
but could also be arranged vertically.
[0032] Also within the scope of the invention is a current limiter
50 according to FIGS. 5 and 6 which can be connected between an
outdoor high voltage line and indoor equipment such as a cable
termination or a gas-insulated substation. It is to be noted that
the cryogenic vessel of limiter 50 and all components directly
associated with the vessel are identical to those in the preceding
figures and the respective reference numerals are used. Also,
limiter 50 corresponds to limiter 35 in FIGS. 3 and 4 in that there
is provided an outdoor bushing 48. All members associated to
bushing 48 are identical to those in FIGS. 3 and 4, and the
respective reference numerals are used in FIGS. 5 and 6.
[0033] On the side of limiter 50 opposite to outdoor bushing 48
there is a disconnecting switch 30 as described with reference to
FIG. 1. As a particular feature of limiter 50 disconnecting switch
30 is contained in an extension 51 of vessel 2 closed by another
disk-type bushing 52 so that the insulating atmosphere of
disconnecting switch 30 is independent of a component 53 to be
coupled to a flange 54 at the outer side of extension 51.
* * * * *